WO 02075312 (Gyros AB) describes a microfluidic device in which there is a microchannel structure which each comprises a separation unit for removing particulate material from a liquid aliquot. The liquid aliquot contains also a solute that in a subsequent step is a reactant in an affinity based assay.
PCT/SE2004/001424, WO 0147638 (Gyros AB), WO 03098302 (Gyros AB), WO 02075775 (Gyros AB), WO 02075775 (Gyros AB) describes various structures for which it has been suggested with upstream processing of a liquid sample followed by downstream processing of the result of the upstream processing, possibly including a determination step.
U.S. Pat. No. 6,632,655 (Caliper), Piyasena et al (Anal. Chem. 76 (2004) 6266-6273) and Buranda et al (Anal. Chem. 74 (2004) 1149-1156) describe a porous bed that comprises segments. The bed is used in multi-analyte assays.
Many samples, such as biological fluid samples, many times contain disturbing substances that are capable of negatively affecting results of reactions between a solute and a reactant immobilized to a porous bed. This has created problems for us in sandwich assays as outlined in WO 02075312 (Gyros AB) and WO 04083108 (Gyros AB), i.e. with the analyte being equal to solute S above. If a substance is disturbing or not or to what degree will depend on kind of sample, among others. A disturbing substance may be a dissolved compound, an aggregate and/or a particulate material including also various kinds of mal-functioning reagents (see below). For biologically derived samples particulate material may be cell debris and the like, lipids etc. The problem encountered may be linked to type of reactants, e.g. analyte. Membrane associated biological analytes are often accompanied by relatively large amounts of particulate material disturbing an assay. Samples from cells, tissue and body fluids are typically difficult to handle in microfluidic devices. There may be heterophilic antibodies that interact with antibody reagents in an undesired manner in immune assays. Reagent compositions may contain forms that disturb the result of an assay, for instance by creating signal responses that are comparable to or higher than normal back ground responses. Labelled reactants may contain forms that have an abnormal density of labelled groups thereby differing sizely and/or chemically from the normally labelled forms.